The present invention relates to an apparatus for correcting the position of flat objects, in particular printed products, arriving overlapped on a conveyor.
An apparatus of this type is disclosed by CH-A-677 778. A position changing device is arranged in the downstream end region of a first conveyor, between conveyor tapes forming the conveying plane. It has two disks which are arranged beside each other in the conveying plane and driven in opposite directions, on which a displacement cam is situated eccentrically in each case. These displacement cams are intended in each case to come into contact with the trailing edge of each object arriving on the first conveyor in an overlapping stream and to accelerate said object in the conveying direction and feed it to the second conveyor. The latter is assigned a braking device which is intended to brake the objects accelerated by the rotation of the discs to the conveying speed of the second conveyor. By coordinating the circumferential speed of the displacement cams to the conveying speed of the first conveyor and the distance between the printed products in the overlapping formation fed, it is possible to achieve the situation in which the distance between the printed products is made uniform, and the printed products can be conveyed away at a phase angle predefined by the further processing means. Connected upstream of the position changing device is a restraining device constructed as a circulating driven pressing band, in order at least to secure the following printed product, in contact with the printed product accelerated by the displacement cams, against being carried along as well. In addition to the risk of damaging the printed products because of the high speeds, accelerations and retardations associated with this apparatus, in particular at a high processing capacity, there is the risk that if there is a very small distance between the trailing edges of successive printed products, the restraining device is ineffective and the printed product following the printed product on which influence has been exerted will be carried along out of synchronism.
An apparatus which can be employed more universally and with careful handling of the objects is disclosed in the earlier international patent application No. PCT/CH98/00561. It has a displacement element which is moved along a movement path by means of a drive, a working section of the movement path extending at least approximately rectilinearly and at least approximately in the conveying direction of the flat objects, such as printed products. In the working section, the displacement element is driven without retardation at a speed which, at the downstream end of the working section, as the objects are transferred to a second conveyor, is at least approximately equal to the conveying speed of this second conveyor. The frequency with which the displacement element is moved through the working section in the conveying direction F is approximately 1.2 to 1.4 times as high as the quotient of the first conveying speed, at which the objects are fed to the working section, and a permissible minimum distance between the trailing edges of successive objects in the overlapping formation arriving. If the distance between the trailing edges of successive objects in the overlapping formation arriving falls below the permissible minimum distance, there is the risk that the next object, following an object too closely, will be carried along and conveyed onward in an uncorrected manner because of the frictional forces.
It is an object of the present invention to develop the apparatus of the generic type in such a way that the security against inadvertently carrying objects along when correcting the position of objects is increased.